The WC-based cemented carbide has been used broadly as tools for cutting of steel and cast iron. Conventionally, various proposals have been made in order to reduce the usage of tungsten, which is a rare metal, and to obtain an intended cutting performance.
For example, a cutting tool made of a composite sintered body, in which the impact resistance and the finished surface gloss of the work material are improved by setting h2/h1 to 0.002-0.02, when h1 is the maximum thickness of the base material in the lamination direction; and h2 is the maximum thickness of the cemented carbide layer of the cutting edge part in the lamination direction, in the cutting tool made of the base material, in which: the cemented carbide layer; and the cermet layer including 15-65 mass % or less of WC and W in total and 80 mass % or more of the iron group metal in the binder phase are Co, are laminated, is proposed in Patent Literature 1 (Japanese Patent (Granted) Publication No. 5185032 (B)).
In addition, a cutting tool made of a composite sintered body, in which the bondability between the cemented carbide layer and the cermet layer is improved; and deformation of the base material after sintering is suppressed by: forming the convexo-concave part having the maximum depth of 50 μm to 500 μm in the boundary between the cemented carbide layer and the cermet layer; and setting h2/h1 to more than 0.02 and 0.4 or less when h1 is the maximum thickness of the base material in the lamination direction; and h2 is the maximum thickness of the cemented carbide layer provided on the rake face side in the lamination direction, in the cutting tool made of the base material, in which: the cemented carbide layer; and the cermet layer including 15-65 mass % or less of WC and W in total and 80 mass % or more of the iron group metal in the binder phase are Co, are laminated, is proposed in Patent Literature 2 (Japanese Patent (Granted) Publication No. 5297381 (B)), for example.
In addition, it is proposed that: the bondability between the cemented carbide and the cermet can be improved; and the wear resistance and the toughness of a cutting tool made of a composite sintered body can be improved in Patent Literature 3 (Japanese Patent (Granted) Publication No. 5413047 (B)), for example, by: improving the; and suppressing deformation generated in sintering, by: setting the convexo-concave state in a specific range in the boundary between the cemented carbide layer and the cermet layer; or adjusting the amounts of binder phases of both layers in specific ranges in producing a tool body by: forming a pressed compact from each of the cemented carbide powder and the cermet powder; laminating these pressed compacts; and sintering in which they are held at 1300-1500° C. for 0.5-3 hours in the vacuum atmosphere.